1. Department of Environmental Science and Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 P. R. China
2. School of Chemistry University of Bristol Bristol BS8 1TS UK
3. College of Environment and Resources Fuzhou University Fuzhou Fujian 350116 P. R. China
4. Bristol Centre for Functional Nanomaterials University of Bristol Bristol BS8 1TL UK